Transition Metal Complexes and Their Applications in Energy Conversion

The rich coordination chemistry of transition metals renders them of interest for broad applications in energy conversion. For example, there is increasing interest in molecular light absorbers such as dye-sensitized photoelectrochemical solar cells (DSSCs) and hybrid inorganic/organic devices. Additionally, the properties of light emitting molecules are the subject of intense research, with applications in organic light emitting diodes (OLEDs) and photosensitisers of energy- and electron-transfer for solar energy conversion. This thesis can be broadly separated into two sections; (1) the study of a macrocyclic cobalt complex and its potential as a catalyst for the conversion of protons into H2 and (2) the synthesis and study of transition metal complexes as phosphorescent dopants for OLEDs. In part 1, the synthesis and characterisation of a series of cobalt compounds coordinated by the macrocyclic biquinazoline ligand, Mabiq, is presented. The solution and solid-state structures of the compounds were examined, alongside the electronic structures of paramagnetic 2 and 3. Electrochemistry data reveals that the reduction of 4 is possible to form a formally Co0 species, which shows promise in its activity with respect to H2 production. In part 2, the synthesis and characterisation of a range of mono- and bimetallic Pt(II) and Ir(III) complexes is presented. A series of readily synthesised tridentate proligands and their resulting complexes is presented that include pseudo-cyclometallating units to allow for mild reaction conditions. The complexes are weakly emissive, with PLQYs in the range 0.1 – 4%, attributed to varying rates of non-radiative decay. Two successful strategies in decreasing non-radiative decay are reported: the replacement of the chloride ancillary ligand with a stronger field acetylide ligand and the development of tetradentate proligands to improve the rigidity of the square planar complexes. The synthesis of hydrazone-based proligands, which offer two N^N^O-coordination sites bridged by a central pyrimidine ring is also reported. Coordination of a second Ir(III) centre results in a 6-fold enhancement of the PLQYs

Measurement of thermal wakes in compressor secondary air systems using low frequency thermocouple data

Experimental temperature measurements are made using two Datatel radio telemetry systems with K-type glass insulated thermocouples inside the Sussex Multiple Cavity Rig (MCR). Currently the MCR supports independent rotational control of both the rotor (disc pack) and a central shaft. The results presented here highlight a novel application whereby the wakes of a set of rotating blocks are captured whilst the rig is at full speed using low frequency data acquisition. This takes advantage of the relative motion of the two telemetry systems to look at flow structures that are usually outside of the frequency domain of the instrumentation

Unravelling perceptions of Eurasian beaver reintroduction in Great Britain

This is the final version. Available from Wiley via the DOI in this record.Data Accessibility: Due to ethical concerns resulting from the permissions given by participants for use of data in this research, supporting data cannot be made openly available. Data are held by the corresponding author.International Union for the Conservation of Nature (IUCN) guidelines state that anticipated impacts must be considered in wildlife reintroduction, including the impacts on humans. Further, since reintroduction projects can be halted by resulting human–wildlife conflicts or human–human conflicts about wildlife, the perceptions of stakeholders and publics are of great importance. Eurasian beaver (Castor fiber) reintroduction is being debated in Great Britain at a devolved level. A decision has already been taken in Scotland to allow beavers already present to remain, while a number of reintroduction trials are taking place in England (both fenced and unfenced). There are also proposals for a reintroduction trial in Wales. We use a sub‐set of results from a nationwide survey (n = 2,759) to identify four social areas that we propose decision‐makers should consider in the debate: key stakeholder perceptions; engagement methods; attitudes towards legal protection and management responsibilities; and support for management techniques. In this paper, we investigate the complex social dimensions of wildlife reintroduction and we argue that emphasis should be placed on the need to recognise societal perceptions of potential management solutions, beyond perceptions of reintroduction itself. This is paramount in order to develop a management strategy that is more likely to garner social support and reduce potential future conflicts, should beaver reintroduction proceed.Natural Environment Research Council (NERC

Operational Trials of Cut-To-Length Harvesting of Poplar in a Mixed Wood Stand

Cut-to-length harvesting systems offer an alternative to conventional mechanical systems for thinning mixedwood stands. We evaluated the performance of a single-grip harvester and forwarder in a poplar-dominated mixedwood stand in Southern Ontario to quantify the effect of tree size and tree form on harvester productivity and harvesting cost, and to assess the damage caused by the harvesting operation to advance regeneration and residual trees. A single-tree selection silvicultural system was used. Individual trees were assigned a form index based on their visual estimates of limb size and stem form. The cut-to-length harvester produced 23.1 m3 per productive machine hour (PMH). Forwarder productivity was 17.2 m3/PMH. The results indicate a significant and positive relationship between harvester productivity and tree size (dbh) and tree form. Tree size (dbh) has the greatest influence on the unit cost of harvesting. At an average 27 cm dbh and extraction distance of 200 m, the stump-to-landing cost was approximately 10 US$/m3. As tree size increased, the unit cost of wood produced decreased. Damage to residual trees and advance regeneration was minimal. The results suggest that single-grip cut-to-length harvesting systems can be effective in managing poplar-dominated mixedwood stands

Sediment and nutrient storage in a beaver engineered wetland

This is the final version of the article.Available from Wiley via the DOI in this record.Beavers, primarily through the building of dams, can deliver significant geomorphic modifications and result in changes to nutrient and sediment fluxes. Research is required to understand the implications and possible benefits of widespread beaver reintroduction across Europe. This study surveyed sediment depth, extent and carbon/nitrogen content in a sequence of beaver pond and dam structures in South West England, where a pair of Eurasian beavers (Castor fiber) were introduced to a controlled 1.8 ha site in 2011. Results showed that the 13 beaver ponds subsequently created hold a total of 101.53 ± 16.24 t of sediment, equating to a normalised average of 71.40 ± 39.65 kg m2. The ponds also hold 15.90 ± 2.50 t of carbon and 0.91 ± 0.15 t of nitrogen within the accumulated pond sediment. The size of beaver pond appeared to be the main control over sediment storage, with larger ponds holding a greater mass of sediment per unit area. Furthermore, position within the site appeared to play a role with the upper‐middle ponds, nearest to the intensively‐farmed headwaters of the catchment, holding a greater amount of sediment. Carbon and nitrogen concentrations in ponds showed no clear trends, but were significantly higher than in stream bed sediment upstream of the site. We estimate that >70% of sediment in the ponds is sourced from the intensively managed grassland catchment upstream, with the remainder from in situ redistribution by beaver activity. While further research is required into the long‐term storage and nutrient cycling within beaver ponds, results indicate that beaver ponds may help to mitigate the negative off‐site impacts of accelerated soil erosion and diffuse pollution from agriculturally dominated landscapes such as the intensively managed grassland in this study.The Mid-Devon Beaver Project is led by Mark Elliott from Devon Wildlife Trust, monitored by the University of Exeter,and funded by Devon Wildlife Trust, University of Exeter and Westland Countryside Stewards. Further support came from NERC grant: NERC/PE/2016_087 and the Wellcome Trust

Vegetation Change and Water, Sediment and Carbon Dynamics in Semi-Arid Environments

This study develops understanding of vegetation change and water, sediment and carbon dynamics in semi-arid environments. Objectives were addressed using an integrated ecohydrological and biogeochemical approach. Fieldwork, over two contrasting grass-woody transitions at the Sevilleta National Wildlife Refuge, New Mexico, USA; quantified vegetation structure, soil structure and the spatial distribution of soil carbon resources. Over both transitions; woody sites showed a lower percentage vegetation cover and a greater heterogeneity in vegetation pattern, soil properties and soil carbon. Soil organic carbon differed in both quantity and source across the sites; with levels higher under vegetation, particularly at the woody sites. Biogeochemical analysis revealed soil organic carbon to be predominantly sourced from grass at the grassland sites. In contrast, at the woody sites soil organic carbon under vegetation patches was predominantly sourced from woody vegetation, whilst inter-patch areas exhibited a strong grass signature. Investigation of function focussed on the hydrological response to intense rainfall events. Rainfall-runoff monitoring showed woody sites to exhibit greater; runoff coefficients, event discharge, eroded sediment and event carbon yields. In contrast to grass sites, biogeochemical analysis showed the loss of organic carbon from woody sites to exhibit a mixed source signal, reflecting the loss of carbon originating from both patch and interpatch areas. To examine the linkages between vegetation structure and hydrological function, a flow length metric was developed to quantify hydrological connectivity; with woody sites shown to have longer mean flow pathways. Furthermore, in addition to rainfall event characteristics, flow pathway lengths were shown to be a significant variable for explaining the variance within fluxes of water, sediment and carbon. Results demonstrating increased event fluxes of sediment and carbon from woody sites have important implications for the quality of semi-arid landscapes and other degrading ecosystems globally. It is thus necessary to translate the understanding of carbon dynamics developed within this study to the landscape scale, so changing fluvial carbon fluxes can be incorporated into carbon budgets, research frameworks and land management strategies at policy-relevant scales.University of ExeterRothamsted Research at North Wyk

Aerial photography collected with a multirotor drone reveals impact of Eurasian beaver reintroduction on ecosystem structure

doi: 10.1139/juvs-2015-0005Copyright © 2015 Canadian Science PublishingBeavers are often described as ecological engineers with an ability to modify the structure and flow of fluvial systems and create complex wetland environments with dams, ponds and canals. Consequently, beaver activity has implications for a wide range of environmental ecosystem services including biodiversity, flood risk mitigation, water quality and sustainable drinking water provision. With the current debate surrounding the reintroduction of beavers into the United Kingdom, it is critical to be able to monitor the impact of beavers upon the environment. This study presents the first proof of concept results showing how a lightweight hexacopter fitted with a simple digital camera can be used to derive orthophoto and digital surface model (DSM) data products at a site where beavers have recently been reintroduced. Early results indicate that analysis of the fine-scale (0.01 m) orthophoto and DSM can be used to identify impacts on the ecosystem structure including the extent of dams and associated ponds, and changes in vegetation structure due to beaver tree felling activity. Unmanned aerial vehicle data acquisition offers an effective toolkit for regular repeat monitoring at fine spatial resolution which is a critical attribute for monitoring rapidly-changing and difficult to access beaver-impacted ecosystems

Related elements in groups

EThOS - Electronic Theses Online ServiceGBUnited Kingdo